Time divided pilot channel detection processing in WCDMA terminal having shared memory

ABSTRACT

A method for operating a Radio Frequency (RF) receiver of a wireless terminal. During a first time interval, an RF front end is enabled and the RF receiver receives and processes an RF signal, e.g., a Wideband Code Division Multiple Access (WCDMA) signal, to produce a baseband signal and to store samples of the baseband signal. During a second time interval that differs from the first time interval, the RF front end is disabled and the RF receiver processes the plurality of samples of the baseband signal of the first time interval to measure signal strengths of a plurality of pilot signals present in the baseband signal of the first time interval. Finally, during a third time interval that differs from the first time interval and the second time interval, the RF front end is enabled and the RF receiver receives and processes an RF signal of the third time interval to extract data there from. Memory is shared between the first, second, and third time intervals for different uses.

BACKGROUND

1. Technical Field

The present invention relates generally to wireless communicationsystems; and more particularly to the processing of communicationsreceived by a wireless terminal in such a wireless communication system.

2. Related Art

Cellular wireless communication systems support wireless communicationservices in many populated areas of the world. Cellular wirelesscommunication systems include a “network infrastructure” that wirelesslycommunicates with wireless terminals within a respective servicecoverage area. The network infrastructure typically includes a pluralityof base stations dispersed throughout the service coverage area, each ofwhich supports wireless communications within a respective cell (or setof sectors). The base stations couple to base station controllers(BSCs), with each BSC serving a plurality of base stations. Each BSCcouples to a mobile switching center (MSC). Each BSC also typicallydirectly or indirectly couples to the Internet.

In operation, each base station communicates with a plurality ofwireless terminals operating in its serviced cell/sectors. A BSC coupledto the base station routes voice communications between the MSC and theserving base station. The MSC routes the voice communication to anotherMSC or to the PSTN. BSCs route data communications between a servicingbase station and a packet data network that may include or couple to theInternet. Transmissions from base stations to wireless terminals arereferred to as “forward link” or “downlink” transmissions whiletransmissions from wireless terminals to base stations are referred toas “reverse link” or “uplink” transmissions. The volume of datatransmitted on the downlink typically exceeds the volume of datatransmitted on the reverse link. Such is the case because data userstypically issue commands to request data from data sources, e.g., webservers, and the web servers provide the data to the wireless terminals.

Wireless links between base stations and their serviced wirelessterminals typically operate according to one (or more) of a plurality ofoperating standards. These operating standards define the manner inwhich the wireless link may be allocated, setup, serviced, and torndown. Popular currently employed cellular standards include the GlobalSystem for Mobile telecommunications (GSM) standards, the North AmericanCode Division Multiple Access (CDMA) standards, and the North AmericanTime Division Multiple Access (TDMA) standards, among others. Theseoperating standards support both voice communications and datacommunications. More recently introduced operating standards include theUniversal Mobile Telecommunications Services (UMTS)/Wideband CDMA(WCDMA) standards. The UMTS/WCDMA standard employs CDMA principles andsupport high throughput, both voice and data. As contrasted to the NorthAmerican CDMA standard, transmissions within a UMTS/WCDMA system are notaligned to a timing reference, i.e., GPS timing reference. Thus,synchronization to a base station by a wireless terminal is morecomplicated in a WCDMA system than in a North American CDMA system. Cellsearching, base station identification, and base station synchronizationconsumes significant processing resources. Such continuous operationscan overload a baseband processing module causing degradation ofperformance and decrease battery life.

BRIEF SUMMARY OF THE INVENTION

The present invention is directed to apparatus and methods of operationthat are further described in the following Brief Description of theDrawings, the Detailed Description of the Invention, and the claims.Other features and advantages of the present invention will becomeapparent from the following detailed description of the invention madewith reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a system diagram illustrating a portion of a cellular wirelesscommunication system that supports wireless terminals operatingaccording to the present invention;

FIG. 2 is a block diagram functionally illustrating a wireless terminalconstructed according to the present invention;

FIG. 3 is a block diagram illustrating components of a basebandprocessing module according to an embodiment of the present invention;

FIG. 4A is a graph illustrating diagrammatically the power spectraldensity of WCDMA RF band(s) supporting multiple RF carriers;

FIG. 4B is a block diagram diagrammatically illustrating the timing ofvarious channels of a WCDMA system employed for cell searching and basestation synchronization according to the present invention;

FIG. 5A is a graph illustrating an example of a multi-path delay spreadat a first time;

FIG. 5B is a graph illustrating the example of the multi-path delayspread of FIG. 5A at a second time;

FIG. 6 is a flow chart illustrating operations of a wireless terminal insearching for, finding, synchronizing to, and receiving data from a basestation according to an embodiment of the present invention;

FIG. 7 is a flow chart illustrating generally operations of a wirelessterminal in searching for, finding, synchronizing to, and receiving datafrom a base station according to another embodiment of the presentinvention; and

FIG. 8 is a block diagram illustrating shared memory operations of an RFreceiver of a wireless terminal according to an embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE DRAWINGS

system 100 that supports wireless terminals operating according to thepresent invention. The cellular wireless communication system 100includes a Public Switched Telephone Network (PSTN) Interface 101, e.g.,Mobile Switching Center, a wireless network packet data network 102 thatincludes GPRS Support Nodes, EDGE Support Nodes, WCDMA Support Nodes,and other components, Radio Network Controllers/Base Station Controllers(RNC/BSCs) 152 and 154, and base stations/node Bs 103, 104, 105, and106. The wireless network packet data network 102 couples to additionalprivate and public packet data networks 114, e.g., the Internet, WANs,LANs, etc. A conventional voice terminal 121 couples to the PSTN 110. AVoice over Internet Protocol (VoIP) terminal 123 and a personal computer125 couple to the Internet/WAN 114. The PSTN Interface 101 couples tothe PSTN 110. Of course, this particular structure may vary from systemto system.

Each of the base stations/node Bs 103-106 services a cell/set of sectorswithin which it supports wireless communications. Wireless links thatinclude both downlink components and reverse link components supportwireless communications between the base stations and their servicedwireless terminals. These wireless links support digital datacommunications, VoIP communications, and digital multimediacommunications. The cellular wireless communication system 100 may alsobe backward compatible in supporting analog operations as well. Thecellular wireless communication system 100 supports one or more of theUMTS/WCDMA standards, the Global System for Mobile telecommunications(GSM) standards, the GSM General Packet Radio Service (GPRS) extensionto GSM, the Enhanced Data rates for GSM (or Global) Evolution (EDGE)standards, one or more Wideband Code Division Multiple Access (WCDMA)standards, and/or various other CDMA standards, TDMA standards and/orFDMA standards, etc.

Wireless terminals 116, 118, 120, 122, 124, 126, 128, and 130 couple tothe cellular wireless communication system 100 via wireless links withthe base stations/node Bs 103-106. As illustrated, wireless terminalsmay include cellular telephones 116 and 118, laptop computers 120 and122, desktop computers 124 and 126, and data terminals 128 and 130.However, the cellular wireless communication system 100 supportscommunications with other types of wireless terminals as well. As isgenerally known, devices such as laptop computers 120 and 122, desktopcomputers 124 and 126, data terminals 128 and 130, and cellulartelephones 116 and 118, are enabled to “surf” the Internet (packet datanetwork) 114, transmit and receive data communications such as email,transmit and receive files, and to perform other data operations. Manyof these data operations have significant download data-raterequirements while the upload data-rate requirements are not as severe.Some or all of the wireless terminals 116-130 are therefore enabled tosupport the EDGE operating standard, the GPRS standard, the UMTS/WCDMAstandards, the HSDPA standards, the WCDMA standards, and/or the GSMstandards.

FIG. 2 is a block diagram functionally illustrating a wireless terminalconstructed according to the present invention. The wireless terminalincludes host processing components 202 and an associated radio 204. Forcellular telephones, the host processing components and the radio 204are contained within a single housing. In some cellular telephones, thehost processing components 202 and some or all of the components of theradio 204 are formed on a single Integrated Circuit (IC). For personaldigital assistants hosts, laptop hosts, and/or personal computer hosts,the radio 204 may reside within an expansion card or upon a mother boardand, therefore, be housed separately from the host processing components202. The host processing components 202 include at least a processingmodule 206, memory 208, radio interface 210, an input interface 212, andan output interface 214. The processing module 206 and memory 208execute instructions to support host terminal functions. For example,for a cellular telephone host device, the processing module 206 performsuser interface operations and executes host software programs amongother operations.

The radio interface 210 allows data to be received from and sent to theradio 204. For data received from the radio 204 (e.g., inbound data),the radio interface 210 provides the data to the processing module 206for further processing and/or routing to the output interface 214. Theoutput interface 214 provides connectivity to an output display devicesuch as a display, monitor, speakers, et cetera such that the receiveddata may be displayed. The radio interface 210 also provides data fromthe processing module 206 to the radio 204. The processing module 206may receive the outbound data from an input device such as a keyboard,keypad, microphone, et cetera via the input interface 212 or generatethe data itself. For data received via the input interface 212, theprocessing module 206 may perform a corresponding host function on thedata and/or route it to the radio 204 via the radio interface 210.

Radio 204 includes a host interface 220, baseband processing module 222(baseband processor) 222, analog-to-digital converter 224,filtering/gain module 226, down conversion module 228, low noiseamplifier 230, local oscillation module 232, memory 234,digital-to-analog converter 236, filtering/gain module 238,up-conversion module 240, power amplifier 242, RX filter module 264, TXfilter module 258, TX/RX switch module 260, and antenna 248. Antenna 248may be a single antenna that is shared by transmit and receive paths(half-duplex) or may include separate antennas for the transmit path andreceive path (full-duplex). The antenna implementation will depend onthe particular standard to which the wireless communication device iscompliant.

The baseband processing module 222 in combination with operationalinstructions stored in memory 234, execute digital receiver functionsand digital transmitter functions. The digital receiver functionsinclude, but are not limited to, digital intermediate frequency tobaseband conversion, demodulation, constellation demapping,descrambling, and/or decoding. The digital transmitter functionsinclude, but are not limited to, encoding, scrambling, constellationmapping, modulation, and/or digital baseband to IF conversion. Thetransmit and receive functions provided by the baseband processingmodule 222 may be implemented using shared processing devices and/orindividual processing devices. Processing devices may includemicroprocessors, micro-controllers, digital signal processors,microcomputers, central processing units, field programmable gatearrays, programmable logic devices, state machines, logic circuitry,analog circuitry, digital circuitry, and/or any device that manipulatessignals (analog and/or digital) based on operational instructions. Thememory 234 may be a single memory device or a plurality of memorydevices. Such a memory device may be a read-only memory, random accessmemory, volatile memory, non-volatile memory, static memory, dynamicmemory, flash memory, and/or any device that stores digital information.Note that when the baseband processing module 222 implements one or moreof its functions via a state machine, analog circuitry, digitalcircuitry, and/or logic circuitry, the memory storing the correspondingoperational instructions is embedded with the circuitry comprising thestate machine, analog circuitry, digital circuitry, and/or logiccircuitry.

In operation, the radio 204 receives outbound data 250 from the hostprocessing components via the host interface 220. The host interface 220routes the outbound data 250 to the baseband processing module 222,which processes the outbound data 250 in accordance with a particularwireless communication standard (e.g., UMTS/WCDMA, GSM, GPRS, EDGE, etcetera) to produce digital transmission formatted data 252. The digitaltransmission formatted data 252 is a digital base-band signal or adigital low IF signal, where the low IF will be in the frequency rangeof zero to a few kilohertz/megahertz.

The digital-to-analog converter 236 converts the digital transmissionformatted data 252 from the digital domain to the analog domain. Thefiltering/gain module 238 filters and/or adjusts the gain of the analogsignal prior to providing it to the up-conversion module 240. Theup-conversion module 240 directly converts the analog baseband or low IFsignal into an RF signal based on a transmitter local oscillation 254provided by local oscillation module 232. The power amplifier 242amplifies the RF signal to produce outbound RF signal 256, which isfiltered by the TX filter module 258. The TX/RX switch module 260receives the amplified and filtered RF signal from the TX filter module258 and provides the output RF signal 256 signal to the antenna 248,which transmits the outbound RF signal 256 to a targeted device such asa base station 103-106.

The radio 204 also receives an inbound RF signal 262, which wastransmitted by a base station via the antenna 248, the TX/RX switchmodule 260, and the RX filter module 264. The low noise amplifier 230receives inbound RF signal 262 and amplifies the inbound RF signal 262to produce an amplified inbound RF signal. The low noise amplifier 230provides the amplified inbound RF signal to the down conversion module228, which converts the amplified inbound RF signal into an inbound lowIF signal or baseband signal based on a receiver local oscillation 266provided by local oscillation module 232. The down conversion module 228provides the inbound low IF signal (or baseband signal) to thefiltering/gain module 226, which filters and/or adjusts the gain of thesignal before providing it to the analog to digital converter 224. Theanalog-to-digital converter 224 converts the filtered inbound low IFsignal (or baseband signal) from the analog domain to the digital domainto produce digital reception formatted data 268. The baseband processingmodule 222 demodulates, demaps, descrambles, and/or decodes the digitalreception formatted data 268 to recapture inbound data 270 in accordancewith the particular wireless communication standard being implemented byradio 204. The host interface 220 provides the recaptured inbound data270 to the host processing components 202 via the radio interface 210.

As the reader will appreciate, all components of the radio 204,including the baseband processing module 222 and the RF front endcomponents may be formed on a single integrated circuit. In anotherconstruct, the baseband processing module 222 and the RF front endcomponents of the radio 204 may be formed on separate integratedcircuits. The radio 204 may be formed on a single integrated circuitalong with the host processing components 202. In still otherembodiments, the baseband processing module 222 and the host processingcomponents 202 may be formed on separate integrated circuits. Thus, allcomponents of FIG. 2 excluding the antenna, display, speakers, et ceteraand keyboard, keypad, microphone, et cetera may be formed on a singleintegrated circuit. Many differing constructs integrated circuitconstructs are possible without departing from the teachings of thepresent invention.

Components of the radio 204 may be enabled and disabled at differingoperational time periods according to embodiments of the presentinvention. For example, the components making up the RF front end of theradio 204 may be turned off from time to time to save power, whichresults in extended battery life for a battery powered handheld device.When the radio 204 is neither transmitting nor receiving information butis performing processing on previously received information and/orinformation that is to be later transmitted, components of the RF frontend of radio 204 may be turned off. In such case, the filtering/gainmodule 226, down conversion module 228, LNA 230, Rx filter module 264,Tx/Rx switch module 260, Tx filter module 258, PA 242, up conversionmodule 240, filtering/gain module 238 and/or local oscillation module234 may be disabled to extend battery life. Typically, these components,referred to herein generally as RF front end components, are turned offwhen the radio 204 is neither transmitting nor receiving information.The ADC 224 and the DAC 236 may also be disabled when the RF front endcomponents are not required for transmit or receive operations. However,the ADC 224 and the DAC 236 may be considered to be part of the basebandprocessing module 222 and remain turned on while the baseband processingmodule 222 is turned on.

According to one particular aspect of the present invention that will bedescribed further herein with reference to FIGS. 6 and 8, RF front endcomponents are selectively enabled and disabled based upon the ongoingoperations of the radio 204. In such case, when the RF front endcomponents are required to transmit or receive information they areenabled. Further, when they are not required to transmit and receiveinformation they are fully or partially disabled. Because the radio 204,when supporting WCDMA operations, is required to continually monitor areceived WCDMA signal to discover and measure the strengths of pilotsignals of corresponding base stations, the baseband processing module222 typically will perform these operations during most time periods.However, in order to reduce the number of circuit components of theradio 204 and to reduce power consumption, when the radio 204 is notactively transmitting or receiving information but is simply discoveringpilot signals, a reduced power mode of operation may be used.

With this reduced power mode of operation, during a first time interval,the RF front end components of the receive path, e.g., 264-222 areenabled to receive a WCDMA RF signal of the first time interval.Further, these components of the RF front end receive path are operableto convert the WCDMA RF signal to a WCDMA baseband signal during thefirst time interval. The ADC 224 of the baseband processing module 222(or separate from the baseband processing module 222), is operable tosample the WCDMA baseband signal during the first time interval toproduce a plurality of samples of the WCDMA signal with first timeintervals. These samples are stored in memory 234.

Then, operation proceeds to a second time interval during components ofthe RF front end are disabled. Herein, when discussing the disabling ofthe RF front end, the RF front end may be fully disabled or partiallydisabled. In any case, at least some of the RF front end components aredisabled so that its full functionality is not enabled, in particularreceive path functionality. During the second time interval, thebaseband processing module 222 processes the plurality of samples of theWCDMA signal to measure signal strengths of a plurality of pilot signalspresent in the WCDMA signal. Then, during a third time interval withdifference from both the first and second time intervals, the RF frontend is enabled again to capture data contained in the WCDMA signal.These operations will be described more fully with reference to FIGS. 6,7 and 8.

FIG. 3 is a block diagram illustrating components of a basebandprocessing module 222 according to an embodiment of the presentinvention. Components of baseband processing module 222 (basebandprocessor) 222 include a processor 302, a memory interface 304, onboardmemory 306, a downlink/uplink interface 308, TX processing components310, and a TX interface 312. The baseband processing module 222 furtherincludes an RX interface 314, a cell searcher module 316, a multi-pathscanner module 318, a rake receiver combiner module 320, and a channeldecoding module 322. The baseband processing module 222 couples in someembodiments to external memory 234. However, in other embodiments,memory 306 services the memory requirements of the baseband processingmodule 222.

As was previously described with reference to FIG. 2, the basebandprocessing module 222 receives outbound data 250 from coupled hostprocessing components 202 and provides inbound data 270 to the coupledhost processing components 202. The baseband processing module 222provides digital formatted transmission data (baseband TX signal) 252 toa coupled RF front end. The baseband processing module 222 receivesdigital reception formatted data (baseband RX signal) 268 from thecoupled RF front end. As was previously described with reference to FIG.2, an ADC 222 produces the digital reception formatted data (baseband RXdata) 268 while the DAC 236 of the RF front end receives the digitaltransmission formatted data (baseband TX signal) 252 from the basebandprocessing module 222. The baseband processing module 222 may includethe ADC 224 and DAC 236 described previously with reference to FIG. 2.However, the ADC 224 and the DAC 236 may be associated with the basebandprocessing module 222 but physically separate from the basebandprocessing module 222.

The downlink/uplink interface 308 is operable to receive the outbounddata 250 from coupled host processing components, e.g., the hostprocessing component 202 via host interface 220. The downlink/uplinkinterface 308 is operable to provide inbound data 270 to the coupledhost processing components 202 via the host interface 220. As the readerwill appreciate, the baseband processing module 222 may be formed on asingle integrated circuit with the other components of radio 204.Alternately, the radio 204 (including the baseband processing module222) may be formed in a single integrated circuit along with the hostprocessing components 202. Thus, in such case, all components of FIG. 2excluding the antenna, display, speakers, et cetera and keyboard,keypad, microphone, et cetera may be formed on a single integratedcircuit. However, in still other embodiments, the baseband processingmodule 222 and the host processing components 202 may be formed on aseparate integrated circuit. Many differing constructs integratedcircuit constructs are possible without departing from the teachings ofthe present invention. TX processing component 310 and TX interface 312communicatively couple to the RF front end as illustrated in FIG. 2 andto the downlink/uplink interface 308. The TX processing components 310and TX interface 312 are operable to receive the outbound data from thedownlink/uplink interface 304, to process the outbound data to producethe baseband TX signal 252 and to output the baseband TX signal 252 tothe RF front end as was described with reference to FIG. 2.

The baseband processing module 222 may receive additional inputs andproduce additional outputs to more than one RF front end. As isgenerally known, diversity path processing requires that an RF receiverof a wireless terminal or base station includes multiple antennas fortransmit and receive diversity operations. In such case, each of theseantennas may be serviced by a corresponding RF front end. When thesemultiple RF front ends are used, the baseband processing module 222interfaces to each of the plurality of RF front ends to transmit data toand receive data from. The methodology of the present invention can beapplied to RF receivers and transmitters having multiple RF front ends.Such will be the case by selectively enabling or disabling receiveand/or transmit components of the RF front ends according to theprinciples previously described with reference to FIG. 2 and those willbe described further with reference to FIGS. 6-8.

FIG. 4A is a graph illustrating diagrammatically the power spectraldensity of WCDMA RF band(s) 400 supporting multiple RF carriers 402,404, and 406. The WCDMA RF band(s) 400 extend across a frequencyspectrum and include WCDMA RF carriers 402, 404, and 406. According toone aspect of the present invention, the cell searcher module 316 of thebaseband processing module 222 of an RF transceiver that supports WCDMAoperations according to the present invention is operable to scan theWCDMA RF band(s) 400 to identify WCDMA RF energy of at least one WCDMAcarrier 402, 404, or 406. During initial cell search operations, thecell searcher module 316 will, in combination with other components ofthe baseband processing module 222, identify a strongest WCDMA carrier,e.g., 404. Then, the cell searcher module 316 synchronizes to WCDMAsignals within the WCDMA carrier 404. These WCDMA signals correspondingto a particular base station cell or sector. In these initial cellsearch synchronization operations, the cell searcher module 316preferably synchronizes to a strongest cell/sector.

WCDMA signals transmitted from multiple base stations/sectors may use acommon WCDMA RF carrier 404. Alternately, the WCDMA signals fromdiffering base stations/sectors may use differing WCDMA carriers, e.g.,402 or 406. According to the present invention, the cell searcher module316 and the baseband processing module 222 are operable to synchronizeto WCDMA signals from differing cells/sectors operating in one or moreof the WCDMA RF bands 402, 404, or 406. Such synchronization operationsoccur not only for initial cell search but for neighbor cell search ordetected cell search operations.

FIG. 4B is a block diagram diagrammatically illustrating the timing ofvarious channels of a WCDMA system employed for cell searching and basestation synchronization according to the present invention. The WCDMAsignal illustrated has a 15 slot frame structure that extends across 10ms in time. The WCDMA signal includes a Synchronization Channel (SCH)and a Common Pilot Channel (CPICH), which are introduced in the downlinkto assist wireless transceivers in performing cell search operations.The SCH is further split into a primary SCH (PSCH) and a secondary SCH(SSCH). The PSCH carries a primary synchronization code (PSC) which ischosen to have good periodic auto correlation properties and thesecondary SCH (SSCH) carries a secondary synchronization code (SSC). ThePSCH and the SSCH are constructed such that their cyclic-shifts areunique so that reliable slot and frame synchronization can be achieved.The PSCH and the SSCH are 256-chips long with special formats and appear1/10 of each time slot. During the rest of the time slot, the PrimaryCommon Control Physical Channel (P-CCPCH) is transmitted. As shown inFIG. 4A, the PSCH and the SSCH are transmitted once in the same positionin every slot. The PSCH code is the same for all time slots, andtherefore is used to detect slot boundary. The SSCH is used to identifyscrambling code group and frame boundary. Thus, the SSCH sequences varyfrom slot to slot and are coded by a code-book with 64 code-words (eachrepresenting a code-group). The CPICH carries pre-defined symbols with afixed rate (30 kbps, hence 10 symbols per time slot) and spreadingfactor of 256. The channelization code for CPICH is fixed to the 0^(th)code.

FIG. 5A is a graph illustrating an example of a multi-path delay spreadat a first time, T1. As is known, in wireless communication systems, atransmitted signal may take various routes in propagating from an RFtransmitter to an RF receiver. Referring briefly again to FIG. 1,transmissions from base station 103 to wireless terminal 116 may takemultiple paths with each of these multiple paths arriving in acorresponding time frame. These multiple received copies of thetransmitted signal are typically referred to as “multi-path” signalcomponents. Referring again to FIG. 5A, an example of a delay spreadthat includes multi-path components and their corresponding signalstrength for time T1 is shown.

Serving cell signal components include multi-path components 508, 510,512, and 514 that are received at respective times with respect to aperiodic reference time. Neighbor cell signal components includemulti-path signal components 516, 518, and 520. Note that the servingcell signal components 504 and neighbor cell signal components arrive atdiffering times with respect to the periodic reference time since theyare not time aligned. As is known, multi-path components of thepropagation channel results in signal arrive at the RF receiver atdifferent times. As is also known, the number of received multi-pathcomponents and the signal strength and signal to interference ratio ofeach multi-path component varies over time.

FIG. 5B is a graph illustrating the example of the multi-path delayspread of FIG. 5A at a second time, T2. Because the characteristics ofthe channel from the RF transmitter to the RF receiver changes over timeso does serving cell path signal components 504 and neighbor cell signalcomponents 506. Thus, for example, the multi-path component 508 of FIG.5B, while having the same time relationship to the periodic referencetime as multi-path component 508 as shown in FIG. 5A, has a greatersignal-to-interference ratio or signal-to-noise ratio than it did inFIG. 5A. Further, multi-path component 510 is missing, multi-pathcomponent 512 is smaller in magnitude, and multi-path component 514 isgreater in magnitude than are their counterparts of FIG. 5B. Inaddition, serving cell signal components 504 include a new multi-pathcomponent 552 that is existent at time T2 but it was not existent attime T1.

The neighbor cell multi-path signal component 506 at time T2 of FIG. 5Balso differ from those at time T1 of FIG. 5A. In such case, multi-pathcomponents 516 and 518 have differing magnitudes at time T2 than theydid at time T1. Further, multi-path component 520 which was strong attime T1 does not exist at time T2. Moreover, new multi-path component554 at time T2 exists where it did not exist at time T1. The cellsearcher module 316, multi-path scanner module 318, and rake receivermodule 320 track the existence of these multi-path components,synchronize to some of these multi-path components, and receive data viaat least some of these multi-path components.

FIG. 6 is a flow chart illustrating operations of a wireless terminal insearching for, finding, synchronizing to, and receiving data from a basestation according to an embodiment of the present invention. Theoperation 600 of FIG. 6 commences with the wireless terminal enabling orturning on an RF front end of its RF receiver (Step 602). The operationsare performed during a first time interval 620. At Step 602, the receivepath components of the RF front end are enabled even though some of thecomponents of the RF front end, such as the transmit components of theRF front end, may be disabled. Thus, at Step 602, the receive pathcomponents of the RF front end are enabled to receive a Wideband CodeDivision Multiple Access (WCDMA) RF signal of the first time interval620. Then, operation includes performing an RF sweep of WCDMA bands ofthe WCDMA RF signal to detect WCDMA energy (Step 604). The operations ofStep 604 are also performed in the first time interval 620. Alsoperformed at Step 604 is the operation of converting the WCDMA RF signalto a WCDMA baseband signal on the first time interval. Further, theoperation at Step 604 includes sampling the WCDMA baseband signal on thefirst time interval to produce a plurality of samples of the WCDMAsignal of the first time interval 620. Finally, at Step 604, theoperation includes storing the plurality of samples of the WCDMA signalof the first time interval 620 in memory.

Then, the operation includes disabling at least a portion of the RFfront end of the RF receiver at the beginning of a second time interval622. Disabling the RF front end of the RF receiver may include fully orpartially disabling RF front end components that were describedpreviously with reference to FIG. 2. Thus, the operation at Step 606 mayinclude disabling RF front end receive path components, all or some ofRF transmit path components, and/or all of both of the RF receive pathand RF transmit path components of the RF front end. The operations atStep 606 of the second time interval 622 may further include disablingone or both of the ADC 224 and the DAC 236 that were illustrated in FIG.2. Operation continues during the second time interval 622 at Step 608with processing the plurality of samples of the WCDMA signal of thefirst time interval in order to measure signal strengths of a pluralityof pilot signals present in the WCDMA signal of the first time interval.In such case, each of the plurality of pilot signals corresponds to aWCDMA RF transmitter.

Operation continues to Step 610 wherein the wireless device determineswhether a communication is to be serviced (Step 610). If nocommunication is to be serviced, operation returns to Step 602 from Step610. However, if communication is to be serviced, as determined at Step610, the wireless terminal enables the RF front end of its RF receiver(RF transceiver) to perform communication operations. Typically at Step610, the wireless terminal enables both receive and transmit paths ofthe RF front end so that they can service both receive and transmitcommunications. The operations of Step 612 correspond to a third timeinterval that differs from both the first time interval and the secondtime interval. Then, the RF device initiates and services communicationsusing a shared memory (Step 614) during the third time interval 624. Themanner in which the shared memory is used will be described further withreference to FIG. 6. The operations of Step 614 include receiving aWCDMA RF signal of the third time interval 624 and converting the WCDMARF signal of the third time interval to a WCDMA baseband signal thirdtime interval 624. The operation of Step 614 further includes samplingthe WCDMA signal of the third time interval 624 to produce a pluralityof samples of the WCDMA signal of the third time interval 624. Then,operation includes storing the plurality of samples of the WCDMA signalof the third time interval in memory and processing the plurality ofsymbol samples of the WCDMA signal of the third time interval to extractdata there from. The operations of Step 614 during the third timeinterval 624 continue until the communication is completed (asdetermined at Step 616). From Step 616, operation returns to Step 604wherein the RF device continues to scan for pilot signals.

The manner in which the shared memory is employed to store a pluralityof samples will be described further with reference to FIG. 8. Forexample, referring to both FIG. 2 and FIG. 6, memory 234 may be employedto store differing information during the first time interval 620 andthe third time interval 624. In such case, efficiencies in the use ofmemory 234 reduce energy consumption and the cost of the wirelessterminal because of reduced memory requirements. As was previouslydescribed with reference to FIG. 3, processing the plurality of samplesof the WCDMA signal of the first time interval 620 may be performed by acell searcher module 316. In such case, the cell searcher moduleperforms the operations of Step 608 of FIG. 6. Further, in initiatingand servicing communications using the shared memory at Step 614, a rakereceiver combiner module 320, as previously described with reference toFIG. 3, may be used. In such case, the rake receiver module 320processes information received from the cell searcher module 316 and/ora multi-path scanner module 318 to locate multi-path components of theWCDMA signal. The rake receiver combiner module 320 operates on aplurality of multi-path components of the WCDMA signal of the third timeinterval 624 identified by the cell searcher module 316 and themulti-path scanner module 318.

Note that the operations 602-616 are shown to be performed duringparticular time intervals. According to the present invention, thesetime intervals 620, 622, and/or 624 may overlap. That is, some ofoperations 604, 606, and/or 608 may occur during both the first timeinterval 620 and the second time interval 622. For example, while the RFFront end is enabled (step 602), processing of the stored samples (step608) may occur. Then, while the operations of step 608 are ongoing, theoperations of step 604 are completed and the operations of step 606 areperformed to disable the RF Front end (step 606). Further, note that theoperations of the present invention apply to communication systems otherthan WCDMA systems, as well.

FIG. 7 is a flow chart illustrating generally operations of a wirelessterminal in searching for, finding, synchronizing to, and receiving datafrom a base station according to another embodiment of the presentinvention. The operations 700 of FIG. 7 are performed by the cellsearcher module 316, the multi-path scanner module 318, and the rakereceiver module 320 of the baseband processing module 222 of the radio204 of a wireless terminal constructed according to the presentinvention. The operations 700 are initiated upon start-up or reset orwhen the RF terminal is otherwise detecting a serving cell within aWCDMA system. Operation commences with the RF transceiver performing anRF sweep of WCDMA RF bands to detect WCDMA energy (Step 702). The RFsweep of the WCDMA RF bands is a collective effort between the RFfront-end components of the RF transceiver radio 204 shown in FIG. 2 aswell as the baseband processing module 222 of the radio 204 of FIG. 2.Referring to FIG. 7 and FIG. 3 jointly, in making the RF sweep of theWCDMA RF bands to detect WCDMA energy, the RF front-end tunes to variousRF channels within the WCDMA RF bands 400 as shown and discussed withreference to FIG. 4A. With particular references to the components ofthe baseband processing module 222, the cell searcher module 316 mayinteract with the processor 302 in order to detect WCDMA energy duringthe RF sweep of the WCDMA RF bands.

After this RF sweep has been completed at Step 702, the processor 302,in cooperation with the cell searcher module 316 and the RF front-endcomponents, identifies a particular RF band, e.g., 404 of FIG. 4A, inwhich to detect and synchronize to a WCDMA signal. The cell searchermodule 316 of the baseband processing module 222 searches for pilotsignals (Step 704). In performing its initial cell search operations,the cell searcher module 316 acquires slot synchronization to the WCDMAsignal, acquires frame synchronization to and identifies a code group ofthe received WCDMA signal based upon correlation with the SSCH of theWCDMA signal and then identifies the scrambling code of the WCDMA signalbased upon correlation with the CPICH of the WCDMA signal.

Operation continues with the cell searcher module 316 passing the timingand scrambling code information to the multi-path scanner module 318(Step 706). This information may be passed directly or via the processor302. The multi-path scanner module 318 then locates and monitorsmulti-path signal components of the WCDMA transmissions (Step 708). Themulti-path scanner module 318 then provides the multi-path componenttiming information to the rake receiver combiner module 320 (Step 710).This information may be passed directly or via the processor 302. Therake receiver combiner module 320 then receives information carried bycontrol and traffic channels of the WCDMA signal of the servingcell/sector (Step 712). The RF transceiver continues to receive controland traffic channel information from a serving cell until it decides toeither find a new serving cell via neighbor search operations, it losesthe signal from the serving cell, or upon another operationaldetermination in which it decides to either terminate receipt of thesignal from the serving cell or the carrier is lost. When the signal islost (Step 714) or in another situation which the RF transceiver decidesto move to a different RF carrier, operation proceeds again to Step 702.However, if the RF transceiver determines that continued operation ofthe particular RF carrier and for the particular serving cell shouldcontinue, operation continues to Step 710 again.

According to the present invention, the operations of Step 702 may beduring the first time interval while the operations of Steps 704 may beduring the second time interval. Further, the operations of Steps 706and 708 may be during the second time interval. Alternately, theoperations of Steps 706 and 708 as well as steps 710 and 712 may beduring the third time interval. In any case, according to the presentinvention, some RF front end components are disabled to reduce powerconsumption during correlation operations of Step 704.

FIG. 8 is a block diagram illustrating shared memory operations of an RFreceiver of a wireless terminal according to an embodiment of thepresent invention. As shown in FIG. 8, a memory 234, previouslydescribed with reference to FIG. 2, has a shared memory component 802.During the first time interval 620, the shared memory 802 is used tostore a plurality of samples therein for pilot strength measurementoperations. Then, during the second time interval 622, the plurality ofsamples for pilot strength measurement operations are accessed from theshared memory 802 and processed by cell searcher module 316, forexample. Then, during the third time interval, when communication isbeing serviced by a radio frequency device of the present invention, theplurality of samples that were employed for pilot strength measurementoperations in the second time interval 622 are purged and the sharedmemory 802 is used for interleaver memory storage.

As one of ordinary skill in the art will appreciate, the terms “operablycoupled” and “communicatively coupled,” as may be used herein, includedirect coupling and indirect coupling via another component, element,circuit, or module where, for indirect coupling, the interveningcomponent, element, circuit, or module does not modify the informationof a signal but may adjust its current level, voltage level, and/orpower level. As one of ordinary skill in the art will also appreciate,inferred coupling (i.e., where one element is coupled to another elementby inference) includes direct and indirect coupling between two elementsin the same manner as “operably coupled” and “communicatively coupled.”

The present invention has also been described above with the aid ofmethod steps illustrating the performance of specified functions andrelationships thereof. The boundaries and sequence of these functionalbuilding blocks and method steps have been arbitrarily defined hereinfor convenience of description. Alternate boundaries and sequences canbe defined so long as the specified functions and relationships areappropriately performed. Any such alternate boundaries or sequences arethus within the scope and spirit of the claimed invention.

The present invention has been described above with the aid offunctional building blocks illustrating the performance of certainsignificant functions. The boundaries of these functional buildingblocks have been arbitrarily defined for convenience of description.Alternate boundaries could be defined as long as the certain significantfunctions are appropriately performed. Similarly, flow diagram blocksmay also have been arbitrarily defined herein to illustrate certainsignificant functionality. To the extent used, the flow diagram blockboundaries and sequence could have been defined otherwise and stillperform the certain significant functionality. Such alternatedefinitions of both functional building blocks and flow diagram blocksand sequences are thus within the scope and spirit of the claimedinvention.

One of average skill in the art will also recognize that the functionalbuilding blocks, and other illustrative blocks, modules and componentsherein, can be implemented as illustrated or by discrete components,application specific integrated circuits, processors executingappropriate software and the like or any combination thereof.

Moreover, although described in detail for purposes of clarity andunderstanding by way of the aforementioned embodiments, the presentinvention is not limited to such embodiments. It will be obvious to oneof average skill in the art that various changes and modifications maybe practiced within the spirit and scope of the invention, as limitedonly by the scope of the appended claims.

1. A method for operating a Radio Frequency (RF) receiver that has an RFfront end and a baseband processing module, the method comprising:during a first time interval: enabling the RF front end to receive an RFsignal of the first time interval; converting the RF signal to abaseband signal of the first time interval; sampling the baseband signalof the first time interval to produce a plurality of samples of thebaseband signal of the first time interval; and storing the plurality ofsamples of the baseband signal of the first time interval in memory;during a second time interval that differs from the first time interval:disabling the RF front end; processing the plurality of samples of thebaseband signal of the first time interval to measure signal strengthsof a plurality of pilot signals present in the RF signal of the firsttime interval, wherein the plurality of samples are processed aplurality of times, each processing time corresponding to a search for apilot signal of a differing RF transmitter; and during a third timeinterval that differs from both the first time interval and the secondtime interval: enabling the RF front end; receiving an RF signal of thethird time interval; converting the RF signal of the third time intervalto a baseband signal of the third time interval; sampling the basebandsignal of the third time interval to produce a plurality of samples ofthe baseband signal of the third time interval; storing the plurality ofsamples of the baseband signal of the third time interval in memory; andprocessing the plurality of samples of the baseband signal of the thirdtime interval to extract data there from, wherein: during the first timeinterval, the plurality of samples of the baseband signal of the firsttime interval are stored in a shared memory that comprises pilot signalsearch memory; during the second time interval, the plurality of samplesof the baseband signal of the first time interval remain stored in theshared memory that comprises the pilot signal search memory; and duringthe third time interval, the plurality of samples of the baseband signalof the first time interval are evicted from the shared memory and theplurality of samples of the baseband signal of the third time intervalare stored in the shared memory that comprises interleaver memory. 2.The method of claim 1, wherein: the RF signal is a Wideband CodeDivision Multiple Access (WCDMA) RF signal; the baseband signal is aWCDMA baseband signal; and each pilot signal corresponds to a multipathcomponent of the WCDMA RF signal.
 3. The method of claim 1, wherein thefirst time interval and the second time interval partially overlap suchthat the RF front end is enabled during a portion of the second timeinterval.
 4. The method of claim 1, wherein processing the plurality ofsamples of the baseband signal of the first time interval to measuresignal strengths of a plurality of pilot signals present in the basebandsignal of the first time interval is performed by a cell searchermodule.
 5. The method of claim 1, wherein processing the baseband signalof the third time interval to extract data there from is performed by arake receiver combiner module.
 6. The method of claim 1, wherein:processing the baseband signal of the third time interval furthercomprises locating a plurality of multi-path components of the basebandsignal of the third time interval; and processing the baseband signal ofthe third time interval to extra data there from further comprises rakeprocessing the plurality of multi-path components of the baseband signalof the third time interval.
 7. A Radio Frequency (RF) receivercomprising: a RF front end; and a baseband processing module coupled tothe RF front end, wherein: during a first time interval: the RF frontend is operable to receive a an RF signal of the first time interval andto convert the RF signal to a baseband signal of the first timeinterval; and the baseband processing module is operable to sample thebaseband signal of the first time interval to produce a plurality ofsamples of the baseband signal of the first time interval and to storethe plurality of samples of the baseband signal of the first timeinterval in memory; during a second time interval that differs from thefirst time interval: the RF front end is disabled; and the basebandprocessing module is operable to process the plurality of samples of thebaseband signal of the first time interval to measure signal strengthsof a plurality of pilot signals present in the baseband signal of thefirst time interval, wherein each pilot signal corresponds to arespective RF transmitter, wherein the plurality of samples areprocessed a plurality of times, each processing time corresponding to asearch for a pilot signal of a differing RF transmitter; and during athird time interval that differs from both the first time interval andthe second time interval: the RF front end is operable to capture an RFsignal of the third time interval and to convert the RF signal of thethird time interval to a baseband signal of the third time interval; thebaseband processing module is operable to sample the baseband signal ofthe third time interval to produce a plurality of samples of thebaseband signal of the third time interval and to process the basebandsignal of the third time interval to extract data there from, wherein:the memory comprises a shared memory; during the first time interval,the plurality of samples of the baseband signal of the first timeinterval are stored in the shared memory; during the second timeinterval, the plurality of samples of the baseband signal of the firsttime interval remain stored in the shared memory; and during the thirdtime interval, the plurality of samples of the baseband signal of thefirst time interval are evicted from the shared memory and the pluralityof samples of the baseband signal of the third time interval are storedin the shared memory, wherein the shared memory comprises: pilot signalsearch memory during the first time interval and the second timeinterval; and interleaver memory during the third time interval.
 8. TheRF receiver of claim 7, wherein: the RF signal is a Wideband CodeDivision Multiple Access (WCDMA) RF signal; the baseband signal is aWCDMA baseband signal; and each pilot signal corresponds to a multipathcomponent of the WCDMA RF signal.
 9. The RF receiver of claim 7, whereinthe first time interval and the second time interval partially overlapsuch that the RF front end is enabled during a portion of the secondtime interval.
 10. The RF receiver of claim 7, wherein the basebandprocessing module comprises a cell searcher module that is operable toprocess the plurality of samples of the baseband signal of the firsttime interval to measure signal strengths of a plurality of pilotsignals present in the baseband signal of the first time interval. 11.The RF receiver of claim 7, wherein the baseband processing modulecomprises a rake receiver combiner module that is operable to processthe baseband signal of the third time interval to extract data therefrom.
 12. The RF receiver of claim 7, wherein the baseband processingmodule comprises: a multi-path scanner module that is operable toprocess the baseband signal of the third time interval to locate aplurality of multi-path components of the baseband signal of the thirdtime interval; and a rake receiver combiner module that is operable toprocess the plurality of multi-path components of the baseband signal ofthe third time interval to extra data there from.